Evaluation of the physical-mechanical properties of low-viscositiy resin composites containing nanofibers or bioactive nanoparticles

Abstract

Dentin replacement nanofiber-reinforced fluid resins (bulk-fillers) and fluid bulk-fill resin composites with Giomer technology represent a new category of materials. Considering that bulk filling resins can show a decline in the mechanical properties of the restoration, mainly due to the decrease in the degree of conversion, which can generate postoperative sensitivity and failure of the restoration, evaluating the physical-mechanical behavior of these two categories of material is necessary. Thus, the present in vitro study will evaluate the surface hardness as a mechanical property and the degree of conversion of a fluid bulk-fill resin composite reinforced by nanofibers and a bulk-fill flow resin with Giomer technology, comparing them with a bulk-fill conventional flowable resin. A total of three groups will be developed: G1= Filtek One bulk-fill resin (3M, ESPE); G2= EverX flow (GC), and G3=Beautiful Flow Plus (Shofu). For surface hardness analysis, samples will be prepared (n=6) using a metallic matrix (4 × 4 mm2), simulating the clinical condition of the insertion of a single increment of bulk resin. Then, the specimens will be stored in the dark for 24 hours. Knoop microhardness will be conducted by a single operator using a microhardness tester (50 KgF will be used for 10 s). In each sample, three indentations (100 µm of distance from each other) will be performed. The average of the three indentations will be calculated at the surface and a percentage (% KHN) obtained. The degree of conversion of the samples (n=5/group) will be carried out by measurements using a Fourier transformed infrared spectroscope (FTIR) with an attenuated total reflectance (ATR) accessory. For the unpolymerized spectrum, 3 ¼l of the fluid resin will be dispensed on the ATR crystal to measure the bands. Then, the sample will be light-activated, according to the manufacturer's instructions and the % of the degree of conversion calculated. After verifying the normality and homogeneity of the data, an appropriate ANOVA test will be performed followed by Tukey's complementary test (5%). If data do not present normality, a specific non-parametric test will be conducted.(AU)